• Journal of computational fluids engineering
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• v.6 no.1
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• pp.1-13
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• 2001

The natural convection heat transfer and solidification in a stratified pool are studied. The flow and heat transfer characteristics in a heat generating pool are compared between single-layered and double-layered pools. And local Nusselt number distributions on outer walls are obtained to consider thermal loads on a vessel wall. The cooling and solidification of Al₂O₃/Fe melt in a hemispherical vessel are simulated to study the mechanism of heat transfer and temperature distribution. A unstructured mesh is chosen for this study because of the non-orthogonality originated from the boundaries of double-layered pool. Interface between the layers is modeled to be fixed. With this assumption mass flux across the interface is neglected, but shear force and heat flux are considered by boundary conditions. The colocated cell-centered finite volume method is used with the Rhie-Chow interpolation to compute cell face velocity. To prevent non-physical solutions near walls in case body force is large the wall pressure is extrapolated by the way to include body force. The numerical solutions calculated by current method show that averaged downward heat flux of the double-layered pool increases compared to single-layered pool and maximum temperature occurs right below the interface of the layers.

• Plant Biotechnology Reports
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• v.5 no.1
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• pp.1-7
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• 2011

Secondary walls have recently drawn research interest as a primary source of sugars for liquid biofuel production. Secondary walls are composed of a complex mixture of the structural polymers cellulose, hemicellulose, and lignin. A matrix of hemicellulose and lignin surrounds the cellulose component of the plant's cell wall in order to protect the cell from enzymatic attacks. Such resistance, along with the variability seen in the proportions of the major components of the mixture, presents process design and operating challenges to the bioconversion of lignocellulosic biomass to fuel. Expanding bioenergy production to the commercial scale will require a significant improvement in the growth of feedstock as well as in its quality. Plant biotechnology offers an efficient means to create "targeted" changes in the chemical and physical properties of the resulting biomass through pathway-specific manipulation of metabolisms. The successful use of the genetic engineering approach largely depends on the development of two enabling tools: (1) the discovery of regulatory genes involved in key pathways that determine the quantity and quality of the biomass, and (2) utility promoters that can drive the expression of the introduced genes in a highly controlled manner spatially and/or temporally. In this review, we summarize the current understanding of the transcriptional regulatory network that controls secondary wall biosynthesis and discuss experimental approaches to developing-xylem-specific utility promoters.

• Journal of the Korean Applied Science and Technology
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• v.30 no.1
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• pp.96-115
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• 2013

This article describes the concept and the trend of antimicrobial coating agents, which will help to establish the direction of the research and development on antimicrobial coating agent. Antimicrobial agents are compounds that inhibit or kill microorganisms. They are classified into inorganic, metallic, low molecular weight organic, natural organic, and polymeric compounds. Antimicrobial coatings are applied to the surface of daily necessities, medical devices, industrial products, electrical appliances, fabrics, and interior building materials, etc. Conventional antibiotics penetrate microbes without damaging bacterial cell walls, leading to drug resistance which polymeric antimicrobials can prevent by disrupting cell walls. Most polymeric antimicrobials are focused on cationic polymers. Improvement in the selectivity and durability of antimicrobials and reduction of their toxicity will come true by more reasonable design of molecular structures and their combination in coating system.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.77-82
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• 1995

With the aim to utilize pine wood(Pinus densiflora Sieb. et Zucc.) as an interior building materials, such as flooring material, monoethylene glycol(MEG) resin solution was impregnated into greenwood. Specimens of three different qualities, that is, normal wood, resinous wood and compression wood, were prepared. Distribution of resin element(phosphorus) in MEG resin solution-impregnated woods and preservative effectiveness against brown rot fungi(Tyromyces palustris and Serpula lacrymans) of these woods were investigated. The results were as follows: 1. The concentration of phosphorus into cell walls of resinous wood and compression wood was lower compared to that of normal wood. This shows that the quality of wood has an influence on the penetration of MEG resin solution into the wood. It was shown from a leaching test that MEG resin could be leached out easily from the cell walls. 2. The resinous wood and compression wood, even without MEG resin solution impregnation had high decay resistance. For normal wood, significant improvement of preservative effectiveness was observed after impregnation of MEG resin solution. It was shown that MEG resin was leached out from the woods after leaching test, resulting in the reduction of preservative effectiveness. From this result, suitability of MEG resin solution-impregnated woods as an interior materials was recognized.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.999-1005
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• 2004

Thermal convection between two horizontal walls kept at small amplitude nonuniform temperatures of the form, $T_L=T_1+a{\Delta}T$ sin kx and $T_U=T_2+b{\Delta}T\;sin(kx-{\beta})$ with a, $b{\ll}1$, is numerically investigated. When the Rayleigh number is small, an upright cell is formed between two walls at ${\beta}=0$; the cell is tilted at ${\beta}={\pi}/2$, and a flow with two-tier-structure cells occurs at ${\beta}={\pi}$. As the Rayleigh number is increased, Nusselt number increases smoothly for ${\beta}=0\;and\;{\pi}/2$, but increases rather steeply for ${\beta}={\pi}$ near the critical Rayleigh number ($Ra_c=1708$). When the wave number is small (k=0.5), multicellular convection occurs over one wave length, for all phase differences, and multiple solutions are found.

• Applied Microscopy
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• v.5 no.1
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• pp.31-43
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• 1975

These studies were carried out to detect the presence of infected virus- like particles and also were observed the ultrastructures of Aspergillus ochraseus isolated from kokja and Korean ginseng. The results of ultrastructures of Aspergillus ochraseus are summarized as follows: 1. In fungal cells, nuclei were enclosed by a irregular double membrane and nucleoli in the nucleus. 2. In cytoplasm, mitochondria, rough endoplasmic reticulum with ribosomes and glycogen were scattering distributed and many lomasomes also observed. 3. The osmiophilic bodies of fungal cells existed in the vesicles. 4. The cell walls were composed of a low electron dense materials. 5, Conidia cell walls were extremely thick and possessed the high electron density of outer coat. The virus-like particles were observed in the hyphae of Penicillium chrysogenum Q-176. These virus-like particles measured $350{\AA}$ in diameter. But strains of Aspergillus ochraseus, showing some vesicle particles were also observed about $800{\AA}$ in diameter in the central region of young fungal hyphae. Based on the results of these experiments, it can not be determined virus particles or not. The further studies to determination of virus particles will be proceeded by the chemical, physical and biological assay methods.

• Journal of the Korean Wood Science and Technology
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• v.32 no.3
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• pp.15-24
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• 2004

The present work was undertaken to investigate the anatomical and chemical characteristics of transgenic poplar down-regulated with antisense OMT gene. Also the distribution of lignin in transgenic poplar trees was investigated at cellular level. No visible abnormal phenotype was observed in the fibers and vessel elements of transgenic poplar. Any marked differences in the staining intensities of Wiesner and Mäule color reaction were not identified in the transgenic poplar. TEM micrographs did not show any staining intensities in the cell walls stained with KMnO₄. Interestingly, the UV spectroscopy of semi-thin sections exhibited a distinct decrease of lignin absorption at 280 nm in the vessel walls, indicating transgenic poplar wood with lower amount of guaiacyl lignin in vessel elements. Chemical composition of antisense OMT poplar was almost identical to that of wild-type poplar. Klason lignin content of transgenic poplar did not show any significant difference from that of the controls. The solid state NMR spectra revealed the transgenic poplar with only slightly more syringyl lignin than the control. The present work showed that antisense OMT gene constructed in the poplar was not enough to reduce the overall content of Klason lignin, and suggested that the expression of transformation was confined to vessel walls.

• BMB Reports
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• v.28 no.5
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• pp.443-450
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• 1995

Cloned staphylococcal peptidoglycan hydrolase was used in determining the physiological characteristics of peptidoglycan hydrolase. This enzyme hydrolyzed the bacterial cell walls and released the N-terminal alanine, but not the reducing groups. This cloned gene product was localized in the cytoplasm of transformed Escherichia coli. Activity gels indicated the enzyme had an Mr of about 54,000, which was consistent with the deduced Mr from sequencing of the cloned gene. The activity bound to CM-cellulose but not DEAE-cellulose resin, indicating it as a basic protein. Enhanced enzyme activity in a low concentration of cations, and inhibited enzyme activity in a solution with dissolved phospholipids, suggested that the activity and the availability of this basic protein may be regulated between negatively charged and positively charged cellular molecules. The activity against boiled crude cell wall was much greater than against purifed cell wall, suggesting protein associated with crude cell wall may aid in the binding of the peptidoglycan hydrolase The cloned peptidoglycan hydrolase showed positive activity on whole cells of some lysostaphin-resistant coagulase-negative staphylococci. The cloned enzyme may be an alternative for lysostaphin for lysis of staphylococci.

• The Korea Journal of Herbology
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• v.20 no.3
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• pp.9-18
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• 2005

Objectives : The purpose of this study is to investigate characteristics of cell morphology of two different agar woods (Aquilaria agallocha Roxburgh (AAR) and imitative agar wood (IAW)) using microscopic techniques. Methods : Both light and scanning electron microscopes were used to observe morphological and histological features of the cell of agar woods collected from commercial products in the market. Results : The cell morphology and tissue arrangements of AAR depending on either the adsorption of resin into vessels or no adsorption of resin were observed to compare these features with those of both IAW and Aquilaria sinensis Gilb (ASG). Conclusions : As a result, the vessels of AAR with the resin adsorption was packed with lots of yellow-brownish materials, which were quite different from those of IAW and ASG. The cell walls were thick, and had well-developed traumatic parenchyma tissues with squared cells of the same height and width, which appeared as a clump of small grains packed.

• Animal cells and systems
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• v.3 no.2
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• pp.215-219
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• 1999

Monoclonal antibody for delta-9-tetrahydrocannabiol (THC Ab), conjugated with protein A-gold, was employed as a probe to detect THC localization in the gland and subjacent cells of chemically fixed bracts of Cannabis. THC was detected in the outer wall of the disc cells, fibrillar matrix, the surface feature of secretory vesicles, and sheath throughout development of the secretory cavity. The probe was absent from vesicles. Label was also present in anticlinal walls of disc cells and walls of dermal and mesophyll cells. Little or no THC Ab was present in disc cells and none were detected in control tissues. This distribution pattern of THC Ab was similar to that in tissues prepared by high pressure cryofixation-cryosubstitution. Consistent association of THC with wall and wall-derived materials suggests that cannnabinoids are synthesized outside the plasma membrane and bound to a wall component, where-upon they are transported to the cavity with wall materials released from the disc cell wall during development of the secretory cavity.